Emailing logfiles repeatedly fails, fills up log with "[email failed] Send hello first" errors

[SemaphoreSlim]

As the subject says. I've been trying to get the mesh router to send emails through the office Exchange server, and everything is set up the same (SMTP port 25, same email account name and password) as several other devices we have sending us daily log file dumps, and they're all working fine but I can never get the MR60s (we have two, at two different sites) to work properly.

I've tried all different setups and no dice. I tried using different ports, I tried turning off the encryption. Nothing works.

I may just give up and get a different system for these sites. It's not worth using them if I can't get logfile dumps like my other IoT systems.

[email failed] Send hello first, Monday, Apr 18,2022 19:04:33
[email failed] Send hello first, Monday, Apr 18,2022 19:04:23
[email failed] Send hello first, Monday, Apr 18,2022 19:01:38
[email failed] Send hello first, Monday, Apr 18,2022 18:50:34